1. Field of the Invention
Apparatuses and methods consistent with the present general inventive concept relate to an image forming apparatus and a control method thereof, and more particularly, to an image forming apparatus which receives an interrupt request from a plurality of image processors, and a control method thereof.
2. Description of the Related Art
A conventional image forming apparatus such as a printer, a scanner, a facsimile and a multi-function device transmits and receives data including an interrupt with respect to a memory through a predetermined data bus. An interrupt is generally an asynchronous signal from hardware indicating the need for attention or change.
More specifically, the image forming apparatus generates a predetermined interrupt signal in response to an interrupt request received from an image processor that processes image data and transmits the interrupt signal to a central processing unit (CPU). Then, the CPU executes an interrupt routine that carries out the operation of the interrupt request corresponding to the received interrupt signal.
A color image forming apparatus, which forms a color image on a print medium, includes a plurality of image processors corresponding to a plurality of colors. While the color image forming apparatus receives a plurality of interrupt requests from a plurality of interrupt sources, the color image forming apparatus essentially functions as a mono image forming apparatus in that it carries out each of the plurality of interrupt requests in sequential order, one at a time. Thus, a time delay occurs when processing the respective interrupt requests.
FIG. 1 is a waveform diagram illustrating the processing of interrupt routines of a conventional image forming apparatus.
For example, the conventional image forming apparatus includes four image processors corresponding to cyan C, magenta M, yellow Y, and black K colors. As illustrated in FIG. 1, if interrupt requests corresponding to the C, M, Y, and K colors are sequentially input at points a, b, c, and d, the image forming apparatus generates an interrupt signal nIRQ corresponding to a first interrupt request INT_K of the color K at the point a, and transmits the interrupt signal nIRQ to the CPU.
The CPU then executes the interrupt routine to lower an interrupt level from a logic value of 1 to a logic value of 0 by the interrupt signal nIRQ.
At a point e, when the interrupt level is restored to a logic value of 1 after the interrupt routine corresponding to the first color K is completed, the image forming apparatus generates an interrupt signal nIRQ corresponding to a second interrupt request INT_M of the color M and transmits the interrupt signal nIRQ to the CPU. Then, the CPU executes the second interrupt routine.
After the second interrupt routine is completed, the CPU executes the third and fourth interrupt routines in a similar way.
As described above, the conventional image forming apparatus sequentially processes the plurality of interrupt requests inputted from the plurality of image processors. Thus, a time delay occurs when processing the interrupt requests.
That is, even if the respective image processors generate the interrupt requests almost simultaneously, the conventional image forming apparatus still processes the generated interrupt requests in sequence (i.e. interrupt request # 1, associated with the respective color first, interrupt request #2 associated with the respective color second etc.), thereby causing time delay when processing the subsequent interrupt requests.
Also, the conventional image forming apparatus executes the individual interrupt routine with respect to each of the plurality of image processors, which requires the repetitive operation of checking the completion of the interrupt routines one by one.
Also, the data bus is occupied for a long time due to the time delay in processing the interrupt requests, thereby delaying processing requests from other devices and lowering the performance of the whole system.